Liquid fuel-burning heater



E. S. DOWNS LIQUID FUEL-BURNING HEATER Filed Oct. 31, 1963 April 6, 1965 INVENTOR. EDGAR 5. DOWNS MAHgl VEY, MILLER 8 RAMBO conditions.

United States Patent 3,176,756 LIQUID FUEL-BURNENG HEATER Edgar S. Downs, Worthington, Ohio, assignor to Burner Development (Iorporation, Worthington, Ghio, a corporation of Uhio Filed Get. 31, 1963, der. No. 320,356 7 Claims. (Cl. l58--4) My invention relates to a liquid fuel-burning heater. It has to do, more particularly, with the burner of a heater of the oil-burning type. It relates to that general type of oil-burning burner which is disclosed generally in my Patent No. 3,029,863 dated April 17, 1962 and which uses a mechanical spinner that receives the oil from a source of supply and throws it outwardly by centrifugal force through a surrounding combustion chamber into contact with an annular wall surface thereof.

In the operation of this type of burner, the oil supplied to the mechanical spinner will be thrown oif as small discrete droplets and so that sufiicient primary air for combustion is supplied with the droplets as they are thrown off the spinner and is intermingled with the droplets to bring about effective combustion of at least part of the oil as it passes radially through the combustion chamber. Although some of the oil burns as droplets in suspension, some of the droplets also reach the outer annular wall of the combustion chamber, and this is especially true in the starting of the burner. According to the present invention, this wall is of special material and structure and is so supported and arranged in the combustion chamber to obtain optimum combustion This annular wall will be absorbent and will, by capillary attraction, absorb the oil and spread it to expose a greater area for evaporation. Also, according to this invention I provide a novel arrangement for supplying air for combustion to the absorbent wall.

According to this present invention, the annular ab-. sorbent wall is made of metal which is composed of short fibers or filaments of metal, such as stainless steel, which are arranged in a layer similar to felt. However, various other metals or alloys may be used. In forming a body of such material, the filaments are arranged in a layer which is compressed and is then heated at a suitable temperature to cause fusion or Welding of the overlying filaments without melting or destroying the physical structure of the filaments. The resulting wall material is a mat of metal which is similar to felt in that it has the overlying metal filaments bonded together. However, it is still porous with a porosity of 95% to 50%,

having interstices between the various filaments and actual pores extending through the material. For the purpose of this invention, I prefer a porosity of approximately 80%. By porosity as used herein is meant: the ratio of voids to the total volume of the body, expressed as a percentage. The interstices provide capillary pockets in the mat for receiving and retaining the oil dropiets I when they reach the mat surface and the pores provide this invention, it should withstand a temperature of 1500 F. Furthermore, even though it is porous and of low density, it still has sutficient physical or structural rigidity and strength that it isfree standing or free supporting to permit it to be used as the annular wall itself in the burner without backing it up with a plate or other backing structure.

In the accompanying drawings, I have illustrated the preferred embodiment of my invention, but it is to be understood that specific details of the burner and heater 3,175,75ll Patented Apr. 6, 1965 ice construction can be varied without departing from basic principles of my invention.

In these drawings:

FIGURE 1 is a longitudinal sectional view illustrating a heater in which my invention is embodied.

FIGURE 2 is an enlarged detail view in axial section of the spinner and associated combustion chamber.

FIGURE 3 is a transverse sectional view taken along line 3-3 of FIGURE 2 through the spinner.

FEGURE 4 is an enlarged transverse sectional view taken along line 4+4 of FIGURE 3.

FIGURE 5 is an enlarged face view of the material used in the annular absorbent wall.

With reference to the drawings, I have illustrated a heater having a general structure like that shown in my Patent No. 3,029,863. This heater is shown as being of the small portable horizontal axis type although it is to be understood that my burner may be mounted in various other types of heaters and with its axis vertical or in other positions. However, with my burner, it is possible to obtain clean and efficient combustion without the use of a stack or chimney and, therefore, it is particularly adaptable to a portable heater.

The heater shown comprises a tubular outer casing 20 which is open at its inlet end 21 and at its outlet end 22. Within the tubular casing 20 and in concentric relationship therewith toward the outlet end thereof is a combustion chamber 23 which is mainly of tubular form and is of smaller diameter. than the casing 20 so that an annular air passageway 25 is provided therebetween. This chamber 23 is provided with a flared outlet end 26 in which is concentrically disposed a cup-shaped baffle member 27 which is of less diameter than the flared end 26 to provide an annular outlet for the combustion.

chamber. The chamber 23 is of less length than the casing 20 to form the fan chamber 28 at the inlet end of the casing Ztl. This chamber 28 has a fan 29 disposed therein which is mounted on a motor shaft 3% driven by an electric motor 31 which is suitably supported concentrically within the chamber 28. The shaft 30 is hollow and receives oil or other liquid through a connection 32 from a suitable source of supply. The fan 29 is of suitable form to draw air into the inlet 21 of the casing 2d and force it forwardly through the burner unit 33 into the combustion chamber 23. The burner unit 33 is disposed at the inlet end of the combustion chamber 23. Suitable igniting means 34 is provided for igniting the oil supplied to the burner. Turning vanes 35 are mounted on the rear of the combustion chamber 23 for straightening the air flow from the propeller fan 29 and building up static pressure behind the combustion chamber. Other details of the heater, not important to this present invention, are illustrated in said patent.

. are for supplying part of the primary air for combustion, which comes from the fan 259, through an annular absorbent ring or burner wall 37 disposed Within the combustion chamber wall. This wall 37 is spaced in- Wardly from the perforated combustion chamber wall by axially spaced spacer rings 37:: thereby providing an annular air chamber'39 between the porous absorbent annular wall 3? and the combustion chamber wall.

The wall 37 is made of a suitable liquid absorbent,

' bustion chamber.

3 heat-resistant felt-like mat material as previously indicated, as will be discussed more in detail later.

Located centrally within the burner chamber formed by the annular wall 37 is a mechanical spinner 30. This spinner is carried by the motor shaft 30 which projects centrally into the burner chamber. This spinner is adapted to throw oil droplets intermingled with air from 'the center of the burner chamber 33 toward the outer annular wall 37. The spinner is associated with a back plate'38 supported within the rear end of the com- It is provided with a central primary air metering hole 38a through which the main supply of primary air is supplied to the burner by the fan 29. The shaft 30 extends forwardly through the opening or hole 38a and is concentric therewith. Openings 41 may be provided through the wall 37 to supply additional air for combustion. They are shown arranged in forward and rearward rows although other arrangements are possible. A conical or flared collar 44 is located in association with the forward edge of the absorbent ring 37 just behind a row of angularly spaced openings 45 in the wall of the combustion chamber 23 which serve as secondary air openings.

The spinner 40 may be of the construction disclosed in said patent and is made of a plurality of parts concentrically mounted on the forward end of the hollow shaft 30. As described in said patent, the spinner 40 will receive the oil from the hollow shaft and form it into droplets. The oil and air mixture created by the spinner is directed outwardly toward the absorbent wall 37.

In the use of this burner, the fan 29 is started and the oil'supply is allowed to reach the spinner 40. The igniter 34 is used to initially ignite this oil and it will be noted that this igniter is adjacent the absorbent ring 37. As indicated above, especially at the time the heater is started,'the oil will reach the absorbent ring 37 and will be absorbed thereby. This oil will be readily ignited. As the burner continues to operate, some of the oil will be ignited before it reaches the ring 37 since it will be thrown off the spinner as droplets interminged with the air supplied at the spinner. This air includes primary air supplied both around and through the spinner, as described in said patent. Additional primary air for combustion is supplied through the wall 37 from the air space 39 outwardly of the absorbent ring 37, the air also being forced by the fan 29 through 5 the openings 36 and into the chamber 39, and eventually through the porous Wall 37. The resulting flame will be caused to rotate or swirl about the spinner 40, especially because of the fan 4% carried thereby. This flame will be constricted as its passes forwardly through the flared baffle 44 and combustion will be further aided by the secondary air openings 45 ahead of the baflle 44 which also receive air from the fan 29.

Any oil thrown off by the spinner 40 which reaches the annular wall37 will be absorbed, spread out by capillary action, and will be readily reevaporated for further combustion. The spinner 4-0 creates a swirling and wiping action of the air and oil mixture around the inner surface of the absorbent wall 37, thus insuring effective evaporation and burning of the oil at the surface of the ring 37.

It is important to use material in the ring 37 which will be very absorbent and heat-resistant.

As previously indicated, the wall 37 is made of a mat of 'metal filaments which are combined into felt like material. The material is preferably made of over- .lying filaments which are pressed together and welded or fused together by heating to .a'suitable temperature ical stiucture of the filaments will be destroyed. An.

3 attempt to illustrate such a mat is made in FIGURE 5 but it will be understood that to accurately illustrateit to 1500 F. The mat of felt-like metal will have sufficient rigidity that it will not be necessary to have a back-up plate to support it in its ownplane. As seen in FIGURE 4, it can be mounted adjacent its forward and rearward edges and the intervening plane of the material can be free of any other support. This will permit more freely passage of air through the metal felt.

Thus, a high degree of capillarity is present in the metal felt ring to provide lateral flow over the face of the ring in sufficient quantity to keep the ring well saturated with fuel. this wet ring provides a strong cooling action due to the latent heat of evaporation of the fuel. This cooling action tends strongly to prevent cracking of the'fuel in the liquid state by lowering the temperature of the disc.

For effective and carbon-free operation, the metal felt ring is thin, not less than .026" and not more than .250" in thickness, and a thickness which I have found very satisfactory is .065". a

It will be further apparent that I have provided a burner structure having many advantages. It has been found in actual practice that when a burner of the type described is incorporated in a heater as indicated, it burns a large quantity of fuel for a given volume of combustion space and does it cleanly without smell or smoke and, therefore, is much more efficient than prior burners. By having the metal felt absorbent ring surrounding the spinner, it is possible to have a horizontalarrangement without danger of oil accumulating in the bottom of the burner but the burner is not limited to a horizontal arrangement. The burner has high performance after fast starting and gives good fire with intense burning and is capable of handling a large volume of fuel in a small combustion space thereby being a low-cost burner compared to its capacity. The spinner throws oil out into the metal felt, especially at the time the burner is started,

and this oil will be absorbed and reevaporated 'from the absorbent ring.

The absorbent ring or wall will receive a'thin line of droplets of oil thrown from the spinner Which strike it along a radial line in the same plane as the spinner and spreads this oil out, toward the front and rear edges of the absorbent ring or wall, thereby increasing the Wetted area of the ring and providing increased surface from which the oil can be evaporated more effectively; The.

vent cracking of fuel in the absorbent material by supply- 7 ing enough oxygen to the fuel immediately and also by cooling the oil in the wall. The secondary air holes downstream from the conical baflle introduce a final amount of air to complete combustion at the proper place along the flame. The conical bafile and the annular baflle or ring upstream therefrom serve to separate burning rich gases from the cold secondary air permitting them to mix gradually and toward the center of the combustion chamber away from the sides of the chamber where their impingement might cause carbon formation and the conical baffle especially serves to direct the burning gases toward the center of the chamber;

Various other advantages will be apparent.

The high rate of evaporation from p According to the provisions of the patent statutes, the principles of this invention have been explained and have been illustrated and described in what is now considered to represent the best embodiment. However, it is to be understood that, within the scope of the appended claims, the invention may bepracticed otherwise than as specifically illustrated and described.

Having thus described my invention, what I claim is:

1. A burner for burning liquid fuel comprising a combustion chamber, a spinner rotatably mounted centrally of the combustion chamber, means for supplying liquid fuel to the spinner, means for rotating the spinner so as to throw off the fuel in the form of droplets into the corn- .bustion chamber, and means within the combustion chamber outwardly of the spinner for receiving and ab-- sorbing any droplets of the liquid fuel which reach it, said means comprising a metal felt composed of superimposed filaments of metal bonded together and containing a multitude of capillary pockets for receiving and retaining the fuel and being porous for the passage or" air therethrough, and means for forcing air therethrough to support combustion.

2. A burner according to claim 1 in which the metal felt has a porosity of 95% to 50%.

3. A burner according to claim 1 in which the metal felt is arranged as a wall which is unsupported throughout the greater portion of its area to facilitate forcing of the air therethrough.

4. A burner for burning liquid fuel comprising an annular combustion chamber, a spinner rotatably mounted at the axis of the combustion chamber, means for supplying liquid fuel to the spinner at the axis thereof, means for rotating the spinner so as to throw off the fuel in the form of droplets outwardly into the combustion chamber, and an annular absorbent wall spaced radially outwardly 6. A burner according to claim 4 wherein the annular wall is provided with opposed axially spaced edges, and supports for the Wall adjacent'the edges only so as to provide an unrestricted wall of metal felt between the supports through which said air can be forced.

7. A burner according to claim 6 in which the annular wall is surrounded by a second annular Wall spaced radially outwardly therefrom to provide an annular air chamber which will receive air from said air forcing means and from which it will be forced through the unrestricted wall of metal felt.

References Cited by the Examiner.

UNITED STATES PATENTS 2,161,536 6/39 Smith 158-4 2,978,323 4/ 61 Schmeckenbecker -211 3,029,863 4/62 Downs 158-4 FOREIGN PATENTS 691,430 5/40 Germany. 727,174 3/55 Great Britain.

JAMES w. WESTHAVER, Primary Examiner.

MEYER PERLIN, Examiner. 

1. A BURNER FOR BURNING LIQUID FUEL COMPRISING A COMBUSTION CHAMBER, A SPINNER ROTATABLY MOUNTED CENTRALLY OF THE COMBUSTION CHAMBER, MEANS FOR SUPPLYING LIQUID FUEL TO THE SPINNER, MEANS FOR ROTATING THE SPINNER SO AS TO THROW OFF THE FUEL IN THE FORM OF DROPLETS INTO THE COMBUSTION CHAMBER, AND MEANS WITHIN THE COMBUSTION CHAMBER OUTWARDLY OF THE SPINNER FOR RECEIVING AND ABSORBING ANY DROPLETS OF THE LIQUID FUEL WHICH REACH IT, SAID MEANS COMPRISING A METAL FELT COMPOSED OF SUPERIMPOSED FILAMENTS OF METAL BOUNDED TOGETHER AND CONTAINING A MULTITUDE OF CAPILLARY POCKETS FOR RECEIVING AND RETAINING THE FUEL AND BEING POROUS FOR THE PASSAGE OF AIR THERETHROUGH, AND MEANS FOR FORCING AIR THERETHROUGH TO SUPPORT COMBUSTION. 